kaled - 6:34 pm on May 28, 2010 (gmt 0)

1. Use cloaking to hide outbound links entirely from search engines. If necessary, create a white-list of domain names for news sites such as the BBC, etc. for which links will not be cloaked.
   
2. Consider maintaining a gray-list of domains that are acceptable but for which links will be cloaked.
   
3. Consider maintaining a black-list of domains that are unacceptable and will be blocked automatically. Redirects could be checked with little difficulty.
   
4. If not on any list, and posted by a new member, either the post or just the link could go into pre-moderation.
   
5. Ensure moderators receive a list of new outbound links (that aren't on any list) and the posts that contain them so that they can be easily checked.
   
6. Make sure everyone knows that outbound links will be cloaked - for new members place it in big bold letters on the sign-up page. For existing members, send out an email or maybe arrange for a popup window to be displayed. Also, consider adding a tooltip hint for each outbound link stating that it will be cloaked (i.e. use the title attribute).